Automatic drafting-digitizing apparatus

ABSTRACT

There is disclosed hereinafter a drafting-digitizing machine for automatically scribing information on sheetlike articles and for digitizing lines, curves, and the like that are scribed on or in sheetlike articles. The machine includes a support assembly for supporting the sheetlike articles and for supporting a scribingscanning head. The head is provided with scribing tools and a photoelectric scanning assembly. In addition, the head is moved automatically by motive powered assemblies under the control of a computer having a plurality of digital input assemblies associated with it for providing a plurality of output signals. Output devices disclosed for producing records concerning the operation of said scribing-scanning head, and an additional output member is provided whereon a TV picture of a line, curve, or the like on a sheetlike article may be observed by the machine operator.

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[72) lnventors Charles H. Little 2,948,470 8/1960 Berkley et a1 250/217X Cleveland; 3,004,166 10/1961 Greene .1 250/202 Waldo H. Kliever,Cleveland Heights; 3,017,552 1/1962 Brouwerm 250/202 X l'l lgfn L- k nCleveland Heights. all 3,214,661 10/1965 Duff 250/202 Ohio 3,278,75010/1966 Eissfeldt 250/202 [21] Appl. No. 798,530 3,356,848 12/1967 Heyck310/8.1 X [22] Filed Dec. 4,1968 3,400,274 9/1968 Hawkins.... 2501235 XDivision ol'Ser. No. 516,059, Dec. 13,1965, 3,500,451 3/1970 Yando310/85 abandoned is a continuum-m- Primary Examiner-Walter Stolwein panof 262590 I963 Attorney-Watts, Hoffmann, Fisher & Heinke abandonedPatented Aug. 3, 1971 [73] Assignee Universal Drafting MachineCorporation Bedtord Heights, Ohio ABSTRACT: There is disclosedhereinafter a drafting-digitiz- [54] AUTOMATIC DRAH-mGDIGI-HZING ingmachine for automatically scribing information on sheet- AppARA-"Js likearticles and for digitizing lines, curves, and the like that 11 Claimsl4 Drawing Fig are scribed on or m sheetllke articles. The machineincludes a support assembly for supporting the sheetlike articles andfor [52] 2501202 supporting a scribing-scanning head. The head isprovided 310/8 with scribing tools and a photoelectric scanningassembly. In [51] m 605! U00 addition, the head is moved automaticallyby motive powered Fleld of Search 250/202, assemblies under the controlofa Computer having a plurality 217 CR, 203 T, 235; 310/8, 8.1. 8.5;318/687, of digital input assemblies associated with it for providing a8 plurality of output signals. Output devices disclosed for producingrecords concerning the operation of said scribing- [56] References cuedscanning head, and an additional output member is provided UNITED STATESPATENTS whereon a TV picture of a line, curve, or the like on a sheet-2,913,584 I 1/1959 Dill 250/217 X like article may be observed by themachine operator.

1 --1so l l z 5 1: i '1 j t/158 I 11 1 1| I J. ow -J1 IIIEV v2 '5 i I fI M t l: u 1" 7 J: 'l ln lf", fl l ZIJI T -s F T. 1 1 Ll t 1 TI 1 LP q Af '1 l l 1 l \l OR IN Bas ATENTEUAUG 3l97l sum 1 UF 9 FIG I INVENTORS'.CHARLES HUBBARD LITTLE WALDO H4 KUEVER EUGENE L. WIEMELS Qs MM, BY gATTORNEYS PATENTEUAUG 3:971 3 597 19 SJLU 2 BF 9 FIG. 2 INVENTORS.

CHARLES HUBBARD LITTLE WALDO H. KUEVER EUGENE L. WEEMELS 5 J ATTORNEYS.

PATENTEU AUG 3 :97: 3 597 519 Sm 3 CF 9 INVENTORg. 240 CHARLES HUBBARDLITTLE WALDO H KUEVER EUGENE L. WlEMELS FIG. IO

WM, W BY 2 M ATTORNEYS Au 3Q 6 1 9 SiiiiT [I BE 9 MANUAL CONTROLS T6 8268 28? 72 l 2 READER M 2 SERVO TELEvIsION COMPUTER ZEED INTERPOLATORELECTRONICS 4 7 RATE 807 'QI2 L x a Y MANUAL I TABLE CONTROLS SERVOS i TE TRAN O C R I TYPE- 3 U E WRITER 78 32 6 1 OICITIZER IEIIIIIIG 841.5514 FIG. 4 L OICITIZER ELECTRONICs I02 I00 92 L 94 9s 2 98 MANUAL IOOKC VELOCITY VELOCITY FVELOCITY J OFF-ON CLOCK COUNTER I: SCALER BUFFER{:IOC OIvIOER *HO LINCREMENTAL 5 COUNTER I I [301i H2 n4 Ax J M 1 I:SIGN s SCALER sCALER GATES llY [18 BUFFER INVENTORS. I224 CHARLESRUROARO LITTLE I wALO0 H I LIEvER EUGENE L wIEMELs BY M f e ATTORNEYS.

RECORDER CHORD POSITION REG I ST E R8 |s2 INCREMENT ACCUMULATORINVENTORS.

ATTORNEYS.

PULSE SHAPER L. WIEMELS COMPUTER CONTROL I Y SERVO ELECT I32 2 x SERVOELECT INTERPOLATOR READER TYPEWRITER RECORD 2 RECORD INCREMENT MANUALCONTROLS START STOP MANUAL- AUTO DIGITIZER POSITION CONTROLS PATENTEI)AUG 3 ISII PROGRAM ENTRY OF FUNCTIONS, ETC.

CHARLES HUBBARD LITTLE WALDO H. KLIEVER EUGENE PHOTO MULT.

PULSE SHAPER TRANSDUCER TRANSDUCER L LINE FOLLOWER PIEZOMOTOR FIG. 7

DRIVER C RYSTAL AUTOMATIC DRAFTING-DIGITIZING APPARATUS RELATEDAPPLICATIONS This application is a division of application, Ser. No.516,059, filed Dec. 23, I965, for Automatic Drafting-DigitizingApparatus, which application is a continuation-in-part of application,Ser. No. 262,590, filed Mar. 4, I963, entitled Drafting Apparatus, nowabandoned.

This invention relates to draftingdigitizing systems responsive to drawnor scribed information in the form of lines, characters, and the like,contained on sheetlike articles. or the like, to produce digital recordsand visual representations of such drawn or scribed information. Thisapparatus is capable of automatic, semiautomatic, and manual operationin modes of operation.

BRIEF DESCRIPTION OF INVENTION This invention is capable, through theuse ofa unique electro-optical system of producing binary coded, and/oralphanumeric data representing the true position and direction of alllines, curves, and other graphi al representations that the machine iscapable ofdrawing, and is also capable offollowing a border existingbetween two or more articles in the same manner as it follows graphicalrepresentations to produce a digital output. Also as a lineiollower themachine, in the preferred embodiment provides its operator with a visualrepresentation of the exact line, curve, etc., being followed as it isbeing followed.

A machine ofthis type is highly desirable in that it is capable ofautomatically following lines, figures and other symbolic informationcontained on blueprints, photostats, drawings and the like for producingthe digital analog of the information seen by the machine so that thisinformation may be used to control: machine tool operations; warehousefunctions and machinery; and other subsequent computerized or automaticfunctions.

This invention provides a new and novel machine that is capable ofproducing automatically, semiautomatically, or manually a binary codedor alphanumeric data record, and/or a visual picture of graphical andcharacter information contained on a sheetlike article ofimpressionbearing material.

This invention further provides a device capable of automatically,rapidly, and accurately following a line or characters scribed on asheetlike article to produce an accurate coded representation, that doesnot contain machine hunt information in the output, ofthe line orcharacter.

This invention further provides a new and novel digitizing machine thatis capable of automatically or semiautomatically, or manually followinga line, character, or other graphical representation marked on asheetlike article to accurately produce a binary coded or alphanumericaldata representation of the true position and direction of the line,character or graphical representation on the sheetlike article.

This invention further provides a new and novel digitizing machine thatis capable of automatically following a line to produce a digitalrepresentation of the line's position and direction, and that is capableof recognizing and automatically responding to ambiguities in the line.

This invention also provides an automatic digitizing device that iscapable of providing an operator remotely located from the device with avisual picture of the information being digitized.

Thi invention also provides a unique elcctro-optical system foranalyzing scribed information contained on a sheetlike article toproduce output data representative ofthe position and direction ofthescribed information on the article.

This invention also provides a new and novel device for automaticallymoving an electro-optical scanner over and along scribed information ona sheetlike article to provide output data, representative of theposition and direction ofa segment of the scribed information as viewedwithin a coordinate system set up in the scanner, for recording, and forcontrolling the rate. direction and position of movement ofsaid device.

This invention still further provides means whereby positionalinformation produced by an electro-optical system motor power means maybe correlated with information representative ofa line segment viewed bythe electro-optical system to cause the electro-optical system toprogressively follow the line under observation.

In order that the above and other objects of this invention may beclearly understood and readily carried into effect, the invention willbe described with reference to the accompanying drawings in which:

FIG. 1 is a pictorial representation of the drafting/digitizing machine;

FIG. 2 is a plan elevation of a section of the supporting means utilizedfor supporting the sheetlike article upon which lines and the like arescribed or are to be scribed and of the movable assemblies utilized formoving scribing tools and digitizing equipment;

FIG. 3 is a side elevation of the section shown in FIG.- 2 and furthershows the electro-optical equipment of the digitizing portion ofthemachine; 1

FIG. 4 is a block diagram of the electrical and optical elements of thedrafting/digitizing machine;

FIG. 5 is a block diagram of the interpolator of FIG. 4;

FIG. 6 is a block diagram of the drafting elements used in thedrafting/digitizing machines;

FIG. 7 is a block diagram of the digitizing elements of thedrafting/digitizing machines;

FIG. 8 is a view of the photoelectric head utilized for providing aphoto-optical output of the scribed information being digitized;

FIG. 9 is a diagrammatic view of a segment of scribed information beingdigitized having a set of coordinates superimposed upon it;

FIG. 10 is a side elevation of a part of the electro-optical systemutilized to view the scribed area being digitized;

FIG. 11 is a view showing a portion of the electro-optical system ofFIG. 10;

FIG. 12 is a block diagram showing the electronics utilized to drive theoptical elements shown in FIG. 10;

FIG. 13 is schematic diagram of the electronics of the system shown inblock form in FIG. 12; and

FIG. 14 is a block diagram showing the electro-optical systems outputlogic and a temporary storage.

Referring now to FIG. 1, the preferred embodiment of thedrafting/digitizing machine and the major components of the machine areshown in pictorial form. The drafting/digitizing machine consists ofseveral major subgroups, utilized for the purpose of producing a drawingand/or producing a digital record oflines and the like marked upon adrawing.

For this purpose, a table 10 is provided for supporting the sheetlikearticles which are to be marked by this apparatus, or which bearmarkings that will be digitized by the apparatus. The table 10 will bedescribed in greater detail below; how ever, it is the subject of ourcopending application and will therefore not be described in greatdetail. A pair of runway beams 12, 14 are shown mounted on the table 10,A pair of movable carriages l6 and 18 are mounted one each on the beams12, 14 respectively for movement along the beams. A third beam, 20, issupported in and carried by the carriages I6 and 18, A third carriage,22, is mounted for movement lengthwise of beam 20, where carriage 22supports the drafting and digitizing instruments, indicated generally asthe unit 23, that constitute part of this invention. The carriage 22also supports a television camera 24, which is connected by a cable 25with the camera electronics 26, The movable carriages 16, I8, and 22 areenergized through electrical conductors contained within theirrespective beams. Other conductors are also carried in the beams for thepurpose of transmitting signals to and from the drafting-digitizing unit23 and other signal responsive devices mounted on the movable carriages.All electrical conductors contained within the beams are cable connectedwith other elements of the system such as a storage program control unit28, and an operator's console 30.

The storage program control unit 28 also communicates with a tapetypewriter unit 32, the function of which will be describedsubsequently.

In the preferred embodiment of the present invention, the stored programcontrol 28 is a real-time, process-control computer suitable through theuse of conversion circuitry to provide one one-thousandth of an inchcontrolled positioning of the movable carriages 16, 18 and 22. The unit28 is a purchased unit, and is manufactured by the Digital EquipmentCorporation. The computer has the capability ofstoring 4,096 words inits internal memory, and may be addressed through various input mediasuch as punched tape, magnetic tape, a punched card reader, magnetictape file, and the tape typewriter 32. As utilized in the preferredembodiment of this invention, the computer is addressed through apunched tape reader for automatic drafting operations, and is addressedfrom the drafting-digitizing unit 23 for automatic digitizingoperations. In addition, the computer is addressed from the tapetypewriter 32 for manual insertion into the computer programs to givesemiautomatic control of drafting-digitizing operations, or through theuse of the tape typewriter 32 to provide manual drafting-digitizingcapability.

As an output unit, or that is, as a digitizing machine, the computer 28may be utilized to print out on the tape typewriter 32, punch a papertape by operating a tape punch, punch cards by operating a card punch,and producing magnetic tape outputs through magnetic recording.

THE SUPPORTING TABLE AND MOVABLE ASSEMBLIES The mechanical andelectronic details of the construction and operation of the table 10,beams l2, l4 and 20, and the .movable assemblies l6, l8, and 22 aregiven in our copending application Ser. No. 262,590, filed Mar. 4, I963.However, in order to understand the operation of the drafting/digitizingmachine of the present invention, within the mechanical framework ofourcopending application, a briefdescription of the table, beams, etc. willbe given below.

Referring now to FIGS. 2 and 3, the movable carriage 22 is shownsupported by and mounted for movement with and along the movable beam20. The beam is supported on and mounted for movement with a secondpowered carriage 16, located at one end of the beam 20 and is similarlysupported for movement at the other end with a third powered carriage18, see FIG. 1. The carriage 16 is mounted for movement along the beam12. The beam 20, carriage l6 and the carriage 18 form a second movableassembly constrained to move at right angles to the direction ofmovement of the carriage 22.

The carriage 22 supports a plurality of drafting and digitizinginstruments and also supports carriage drive and digitizing apparatusfor moving the carriage along the beam 20 and for providing digitaloutput information concerning the position of the carriage on the beam.In a like manner the carriages l6, 18, also support drive apparatus, andin addition a positional digitizing device is mounted on carriage 16.

The movable assemblies and beams are supported by the table 10. Thetable is provided with a plurality of channel members 34 for supportinga table top 36 and bracket members 38, only one of which is shown;details of the table construction are given in our copendingapplication. The beams l2, 14 are rigidly attached to the bracketmembers 38 so that the movable carriages lie substantially in a plane.The table top 36 also supports a vacuum chuck 40. The top ofthe chuck isused as a supporting surface for shcetlike articles such as drawingpaper, sheet metal and the like. A sheet of marking material 42 is shownin FIG. 2.

The carriages l6, l8, and 22 are powered by servomotors 44, 46 and 48respectively. The servomotors'are utilized for the purpose of drivingtheir respective carriages along their respective beams to provide thedrafting/digitizing apparatus 23 supported on carriage 22 with motion inboth the X and Y directions. All servomotors are energized throughcurrent conductors carried by the beams 12, 14, and 20. In this mannerthe drafting/digitizing apparatus is caused to move to any point on thetable. It will be obvious to those skilled in the art that a fourth beamcould be supported by the carriage 22 so as to be mounted verticallyperpendicular to the beam 20 to support a fourth powered carriage. insuch an event the drafting/digitizing apparatus would be mounted on thefourth carriage to provide the system apparatus with the ability to movealong three axes instead of the two axes shown in the drawings.

in the embodiment shown, the direction of movement of carriage 22 isarbitrarily designated as movement along the Y axis ofa Cartesiancoordinate system and movement along the beams 12, 14 is designated asmovement along the X axis. ln a like manner, any spot on a beam 12 or 14may be designated as the zero point of the coordinate system and in thepreferred embodiment this point was chosen as a stop located near thelower right-hand corner ofthe table 10.

A synchro system is provided for maintaining beam 20 perpendicular tobeams 12, 14. For this purpose a synchro transmitter 50 is mounted oncarriage l6 and a synchro receiver 52 is mounted on carriage 22,

lncremental digital feedback information regarding the position of thedrafting/digitizing apparatus on the table 10 is obtained from a pair ofdigital transducers 54, 56 which may be of the type described in our USPat. No. 3,009,141 of Nov. ll, 1961. Transducer 54 is mounted formovement on carriage 22 and is keyed to beam 20, and transducer 56 ismounted on carriage 16 or in the alternative, may be mounted on carriagel8, and keyed to beam 12, or if the alternative is used, to beam 14. Thetransducers 54,56 generate binary information indicative of the positionof the carriages on the beams, their rate of travel, and their directionof travel. This information is applied through incremental accumulatorsto the computer 28 and is also applied to the servomotor elec tronics.

As stated the carriage 22 supports a plurality of instruments necessaryfor producing drawings on article 42, or in the alternative forproviding digital output information relative to markings carried byarticle 42. The drafting-digitizing instruments are mounted in thedrafting-digitizing unit 23, also referred to as the stylus head whichis carried by and supported for vertical movement on the carriage 22.The stylus head mounts a stylus turret 60 over the sheetlike article 42.The turret may contain one or more stylus members which may be pens orother scribers, and the like. The turret may be held in a fixed positionby the stylus head. It may be indexable in discrete steps around an axisof movement within the stylus head, or it may rotate freely within thestylus head. The stylii are mounted for vertical movement in the turret60. When they are activated to contact the article 42 they may be givenlinear or rotary motion relative to the article. The digitizing unit 62comprising a photoelectric scanning unit 64 and the TV camera 24 is alsosupported by the stylus head 58 and carriage 22. A detailed discussionof the digitizing unit 62 will be given subsequently.

SYSTEMS CONTROL Referring now to FIG. 4, the input and output devices,the computer, the input-output electronics for the computer, and thetable, drafting-digitizing apparatus. and related equipment have beenshown in a simplified block diagram. It is the purpose of the apparatusand circuits shown in FIG. 4 to convey information to and away from thedrafting table, that is to say, it is the purpose of these circuits tosupply information to cause a drawing or scribing operation to beperformed on a shcctlike article carried by the table 10, and for theinstruments to scan a shectlike article to convert information containedon the article in the form of characters, lines, and the like, intodigital information and pass this information to the computer where itis processed and finally outputed as a recording or the like.

The computer 28 when used in a drafting operation, may receiveinformation from any of several sources ofinput information as shown inFIG. 4, e.g., the computer may accept the output of a reader 68, whichmay be coded in standard EIA code, binary coded decimal, word addressformat, and absolute or incremental. The reader 68 in the preferredembodiment is a punched tape reader, which operates at 300 c.p.s.,however, the reader could also be a magnetic tape reader for operatingoff IBM seven-channel and nine-channel tapes, and may in fact be anyconventional reader utilized as an input to a computer. The computer maybe also addressed from the tape typewriter 32, shown in FIG. 1 and alsoshown as a block in FIG. 4, and may be further addressed through aplurality of switching controls 70, located at the operators console 30of FIG. I. Most input information is entered through the reader 68 orthe typewriter 32 or both.

The computer 28 is a general purpose parallel computer having a 4,096word memory but which can be extended to a 32 K word memory and isutilized for the purpose of controlling the operation of thedrafting/digitizing apparatus mounted on carriage 22, in combinationwith an interpolator 72, connected to the output ofthe computer.Generally speaking, the computer utilizes input information to determinethe direction of travel to be taken by the drafting/digitizing apparatusand the rate or feed rate at which the apparatus is to be moved. Morespecifically, the computer determines from input information whether thedrafting instrumentalities are to draw lines, circles, parabolas, andthe like, or that is to say, to perform linear interpolation, circularinterpolation, or parabolic interpolation, which information iseventually transmitted to the servomechanisms after digital to analogconversion. In addition, the computer is utilized to store alphanumericand symbol information, which may be addressed through the use ofg and dcodes for the purpose of having the drafting instrumentalities drawcharacters and/or standardized symbols. The computer also is used tostore scaling factors of 0.00l x to l()0.0 inches along both axes whichallows independent scaling for each ofthe drawing axes.

The computer 28 may be also controlled to generate informationutilizable by the drafting instrumentalities to produce dashed lines,centerlines, phantom lines, and center locations, from either the tapeor manual input modes by controlling the operation of the turret andstylii.

The servos can cause the drafting instrumentality to operate at a rateof anywhere from O to 400 i.p.m. which rate is dependent upon the feedrate number determined by the computer in response to inputs from eitherthe reader or typewriter. In addition, the reader can be caused to readl0 blocks ahead, of information being processed for servocontrol todetermine whether or not a sharp corner or other discontinuity is to bedrawn, in which event the feed rate wbuld be automatically changed tocompensate for the discontinuity when it occurs. In this manner, thedrafting instrumentalities can produce sharp corners without roundingand thus the problem ofdrafting overshoot is eliminated. Thus, thesystem is capable of handling tapes that are not provided with feedrates. I

The computer 28 also may provide output displays at the control console30, FIG. I, or at the computer cabinet through the use ofa displaylighting panel 74, which can be utilized to indicate to the operator theposition ofthe drafting and digitizing instrumentalities relative to thedrawing or digitizing surface 42, and can be used to indicate the tapesequence.

The interpolator 72 will be described relative to a block diagramsubsequently, but it is sufficient to say at this point that it providesboth directional movement command signals and rate of movement commandsignals to the servo electronics 76. The servo electronics do notconstitute part of this invention, and are described in detail in ourcopending application Ser. No. 262590, filed Mar. 3, I963. It issufficient for the purpose of this invention to state that the servoelectronics 76 receives binary information from the interpolator 72, andin addition, receive binary information from the transducers 54, 56,FIGS. 2, 3, which are shown as a transducer block 78 in FIG. 4. Inputinformation from the interpolator and from the transducer is combined inthe servo electronics 76, to produce modulate a sine wave or continuousinformation signal is utilized to drive the-servos 44, 46, and 48 whichhave been shown combined as the servos in FIG. 4. The servos 80 areshown in FIG. 4 as applying a mechanical output to the table 10; theoutput shown is the drafting operation.

As mentioned heretofore, the carriage 22 also carries the digitizingunit 62 which is shown in block form in FIG. 4. The digitizing unit willbe referred to as the photoelectric head 62. Although as mentionedearlier, the digitizing unit 62 includes the television camera 66; thecomplete television system has been shown as a separate block 82 in FIG.4 and in FIG. 7 for convenience. The digitizing unit is a photoelectricsystem utilized for the purpose of converting information contained asmarkings such as lines, characters and the like on the table 10 intopulse information which is fed to the computer 28 through digitizerelectronics 84. A feedback path 85 from the digitizer electronics to theunit 62 has been shown and will be described below, but basicallyfeedback is utilized for controlling the mechanical operation of thedigitizing unit. The electronics and digitizing unit will also bedescribed in detail below. The signal output from the digitizerelectronics 84 is fed to the computer 28 for the purpose of convertingthe information produced in the digitizer into standard EIA, binarycoded decimal, and the like codes, which information is utilized toproduce output recordings. An output recorder 86 is connected to thecomputer 28, and may be a paper tape punch, a typewriter, a magnetictape recorder, a card punch or the like. In addition, informationproduced by the photoelectric head 62 and its electronics 84 is utilizedto control the operations of the servos 80 in the same manner thatinformation inputted from the typewriter 32 and reader 68 was used tocontrol the servos 80.

The television system represented by the box 82 and shown mechanicallyconnected to the table H) in FIG. 4 consists ofa camera 66 as shown inFIG. 2 of the drawings mounted on the photoelectric head 62; cameraelectronics including amplifying circuits and television routingcircuits are supported on the table 10, and a receiver 88 is located atthe operator's console 30, FIG. 1. The picture produced on the receiver88 is an en- Iarged view of that portion of the sheetlike article beingmarked or being digitized, or that is that portion of the article thatis directly under the digitizer unit 62. The manner in which the imageis obtained will be described below.

Manual controls 90 for digitizing operations are also prothe computer 28and the servo electronics 76. These controls and their operation will bedescribed subsequently, but it is sufficient to say at this point thatthey are utilized for manually controlling the movements of thedigitizer unit 62. They are used to drive the servo electronics andhence the digitizer follower unit-62 over the table surface 10 so thatan operator can choose between allowing the digitizing unit toautomatically output information relative to the marked article carriedby the table 10 and in addition, they are utilized by the operator forcorrecting ambiguous situations occurring with respect to markings onthe sheetlike article on table 10. Finally, they, are utilized by theoperator for printing out or causing the computer to print outinformation relative to points seen by the operator as viewed in hiscathode-ray tube display 88.

The interpolator 72 shown in FIG. 4 has been shown in greater detail inFIG. 5 as a block diagram in that the circuits utilized for the purposeof combining feed rate and distance of movement command information fromthe computer in each of the X and Y directions are in themselves old inthe computer art. It is the function of the interpolator to combineinformation as to distance oftravel to be covered by the drafting anddigitizing instrumentalities on the table 10 with information as to therate at which the instrumentalities are to move. To accomplish thisobject, the computer controls a plurality of scaling devices with binaryinformation received from the reader and from the servo electronics inthe case of drafting and from the table and servo electronics in thecase ofdigitizing.

The computer operates a conventional 100 kc. clock 92 over aninput-output transfer command line 94; the clock 92 is also providedwith a manual off-on control at the operator's console. The clock isutilized for the purpose of generating a train of pulses at a constantrepetition rate of 100 kc. where the pulses are utilized to drive acounter 96. The counter 96 is a conventional incremental counter andcounts 100 k, pulses, and for any particular feed rate operation quitsafter counting for one feed rate number. Simultaneously, the computer 28over a second input-output transfer line 98 feeds velocity commandinformation known as the feed rate number to a velocity buffer 100. Thevelocity buffer 100 is a serial read in, parallel readout register andis utilized for time buffering the computer to subsequent electronicsoperating at lower speeds. More specifically, the buffer 100 outputs sixbits to selectively operate a plurality of carry gates in a velocityscaler 102. The velocity scaler 102 is also operated on the other end bythe velocity counter 96 where the counter 96 operates a proportionalcounter in the sealer; the output of the proportional counter isconnected to the other inputs of the carry gates which in the preferredembodiment are utilized to provide 64 feed rate numbers.

The velocity sealer 102 in turn operates a conventional chain of binaryflip-flops operating as a divider 104 over a line 106. ln the preferredembodiment, divider 104 is a scale of eight divider although it is to berecognized that for the purpose of this description the scale of eightdivider is utilized in conjunction with a specific computer and with aspecific servo electronics system and that for other systems utilizingdifferent computers and different electronics might call for a different scale of division. The number outputted from the divider 104 isthe feed rate number utilized by the servo electronics to drive theservomotors at some speed between and 400 inches per minute.

The divider 104 is operatively connected to an incremental counter 108over line 110. The incremental counter is a series of binary flip-flopsand is utilized for the purpose of counting 256 pulses from the feedrate number. The output of the counter 108 is connected over a pair oflines to a pair of dimension sealers 112 and 114. The scalers 112 and114 are similar to the scaler 102. The output of the incremental counteris applied to proportional counters in each of the two sealers.

Dimensional input information as to the distance to be traveled alongeither the X and Y axis is applied from the com puter 28 to a pair ofbuffer registers 116 and 118 over inputoutput transfer lines 120 and 122respectively. The buffers 116 and 118 are serial input, parallel outputregisters utilized for matching the computer to the interpolater andthence to the servo electronics. The buffers 116, 118 operateconventional carry gates in each of the twodimensional sealers 112, 114where the carry gates are connected to the proportional countersmentioned previously. 1n this manner, the sealers 112 and 114 are set upby the computer to handle both dimensional and velocity informationwhich information is utilized by the servo electronics.

The output ofthe scaler 112 is applied over a line 124 to a plurality ofsine gates 126. The output of the scaler 114 is applied over a line 128to the sine gates 126. The sine gates are conventional AND gates. For atwo-directional machine four gates are required, two gates for eachdirection of travel, thus giving the machine the capability to move intwo directions along each axes of movement. The gates are selectivelyoperated by the computer over a line 130 where the com uter selects thedirection of movement along the'b'eams of H05. 1, 2, and 3 byselectively operating the gates 129. The sintgates are connected to theservo electronics 76 shown in FIG. 4 of the drawings and described indetail in our copending applicattion.

Referring now to FIG. 6, the transfer of information for a draftingoperation and the circuits utilized for the transfer are shown in blockdiagram form. The manual controls 70, reader 68 and typewriter 32 arethe same as shown and described with reference to FIG. 4 where theyoperate as input devices for the transferral of command information tothe computer 28. As has been explained with reference to FIG. 5, thecomputer 28 transfers information to the interpolator 72 which combinesinformation as to feed rate number and dimensional movement along twoaxes and which is also utilized for the purpose of buffering between thecomputer and servo electronics. Servo command data is outputted from theinterpolator 72 through the sine gates 126 to two separate servoelectronic units 132, 134 along the signal lines 133, 135 respectively.The units 132, 134 were shown as the combined unit 76 in FIG. 4. As hasbeen stated heretofore, the operation of the servo electronic units isfully described in our copending application. A brief description oftheir operation will be given for the purpose of understanding theoperation of this invention.

Both servo electronics 132 and servo electronics 134 are similar intheir construction and operation and are utilized for the purpose ofconverting binary information to sinusoidal or other continuousinformation for driving the respective servos. The units 132 and 134 arealso connected to a pair of digital transducers 136 and 138 respectivelywhere the transducers are mechanically connected to the table 10 toproduce digital information representative of the position and rate oftravel of the servos over the table. This information is combined withcommand information from the computer in the servo electronics and iscounted and applied to control a pair of modulators which modulatorsprovide continuous output signals corresponding to the digitalinformation applied to the counters. The modulators are operativelyconnected to a pair of servos 140 and 142 through conventionalamplifiers where the servo 140 is connected in the output of the servoelectronics 132 and the servo 142 is connected in the output of theservo electronics 134.

The digital transducers 136, 138 are also connected to the computer 287The computer utilizes the transducer signals to provide a numericaldisplay at its output apparatus 74 of the position of the draftinginstrumentalities on the table. In a like manner, the computer 28 canalso operate output recorders 86, as mentioned earlier, for the purposeof recording the position of the drafting instrumentalities as they aremoved over the table.

The computer 28 is also used to operate auxiliary command circuits 144over a line 146. The auxiliary command circuits 144 supply operatingcommands to the stylus turret 60 to cause it to be indexed or rotated,and they supply stylus updown and rotate signals to stylii 147 carriedin the turret 60. The manual control panel 70 is provided with stylusand stylus turret override switches. These switches are used by theoperator over command line 148 to override computer control ofthe namedfunctions.

Referring now to H6. 7, a preferred embodiment of the digitizingapparatus and electronics that constitute a part of this invention isshown in block diagram form. The digitizer system 62 will hereinafter bereferred to as either the photoelectric head, scanning unit or linefollower 62. The scanning unit is mounted for movement over a surfacecontaining a marking or markings such as lines. The photoelectric head62 includes an optical system which is designed so that in any givenscanning period a discrete portion of the total surface of the article42 of FIG. 1 is under the photoelectric head 62. Thus, the scanning unit62 views a discrete segment of a line, where the line may be a singleline or one ofa plurality of lines, in any given scanning period. Themanner in which the photoelectric head 62 is made to move so as toconstantly view different and overlapping discrete elements of the linewill be described below. lt is sufficient for the purpose of describingthe digitizing apparatus generally to state that the output of the linefollower 62 is such as to produce digital information that is utilizedin conjunction with a second source of such information to cause thepowered carriages 16, 18,22 of FIG. 1 to drive the photoelectric head 62in discrete steps of 0.0010 inch over and along a line where thephotoelectric head 62 views a round area having a diameter ofapproximately 0.012 inch as the area moves around the inside peripheryof a circle having a diameter of 0.080 inch in a scanning cycle. Ascanning cycle is defined as that time it takes the round area to makeone complete sweep within the larger circle. The round area and largercircle are shown in FIG. 10 and a full explanation ofa scanning cyclewill appear below. it will, ofcourse, be understood that other sizedstepping movements and scanning configurations could be substituted forthose utilized in the preferred embodiment.

The photoelectric head 62 determines the position and direction of aline segment, i.e., the portion of the line, located within the totalarea under the photoelectric head during a scanning cycle, and the head10 provides output information pertaining to the position and directionof the line segment within said total area; and it provides anelectronic reference signal generated by an optical system containedwithin the photoelectric head for the purpose of orienting the computer28 as to the position and direction of a line as seen by thephotoelectric head. The optical elements of the photoelectric head 62are mechanically coupled to a piezomotor 150 where the motor 150 isdriven by a crystal driver 152. The piezomotor 150 consists of apiezoelectric ceramic having a mirror mounted on the end thereof wherethe mirror is included as part of the optical path within thephotoelectric head 62. The operation and structural details of thepiezomotor 150 and crystal driver 152 will be described in greaterdetail subsequently but it is pertinent to say at this point that thepiezomotor 150 is fundamental to the operation ofthe line follower inthat it functions when driven by the crystal driver 152 so as to definethe geometric configuration and area of a given incremental scanningstep so as to cause the photoelectric head 62 to provide informationaldata representative of the position and direction of line segment underobservation during an incremental step. The crystal driver 152 producesthe reference signal mentioned above, which signal is applied to a pulseshaper 154 where it is squared and applied over a reference signal line155 to the input of a chord position register 156 where the referencesignal is temporarily stored.

The round area being viewed by the line follower 62 as the area scansthe line segment within the larger circle produces signals every timethe round area crosses the line. These signals are converted into theirelectrical equivalent by a photomultiplier tube 158. The photomultipliertube 158 is mechanically part of the line follower 62 and has been shownas a separate block in FIG. 7 for convenience only. The electricalpulses produced by the photomultiplier 158 are squared in a pulse shaper160 and stored in the chord position register 156. The operation anddetails of the pulse shapers 154 and 160 and the chord position register156 will be described in greater detail below. They are utilized toproduce binary information pertaining to the line being followed to beused by the computer 28 so that the computer may cause the outputrecorder 86 to produce a permanent record of the position and directionof the line segment scanned, and to allow the computer to command thedirection. rate and distance of movement ofthe scanning head 62.

The informational data readout ofthe chord register 156 by the computer28 is averaged by the computer 28 to produce a mathematical straightline approximation of the line segment seen by the photoelectric head62. Since the line segment viewed by the photoelectric head 62 isextremely small. and in the preferred embodiment of the inventionconsisted of that portion of the total line that intersects a circle of0.0ii0-inch diameter at two points on the circuml'crenc' of the circle,the approximation to a straight line is extremely accurate because thelongest chord from which positional and directional data is obtained isat most 0.080 inch in length.

As stated heretofore, the computer 28 produces incremental informationwhich is utilized to step the photoelectric head 62 forward to scansubsequent discrete areas along the line being followed. As has beenstated heretofore, the photoelectric head 62 is mounted for movement oncarriage 22. H05. 1, 2, 3, and is caused to move through the operationof the X and Y servos 140, 142 as described with reference to FIG. 6.For digitizing operations, the carriages are completely controlled as todirection. rate and distance of operation by the computer 28 through itscontrol of the servos. This operation is different from the draftingoperation in that the primary source of information supplied to thecomputer originates from the drawing or other marked article. Thecomputer 28 provides binary data output to the interpolator 72 whichdata is representative of the position and direction of theapproximation of the line segment in the area under observation and theposition of the servos 140 and 142. That information consists of thedeviation of the line segment from the direction of travel of the linefollower 62 as computed with respect to the next preceding approximationof a line segment. The computer 28 calculates this deviation signal andprovides correctional output information to the interpolator 72 whichinformation is utilized to drive the servos 140 and 142 through theirrespective input electronic units 132 and 134. A mechanical connectionis shown between the servos 140 and 142 to the scanner unit 62 for thepurpose of indicating that the servos control the direction of movementof the scanner unit. in order to compute the deviational signal, thetransducers 1-36 and 138 provide continuous output binaryrepresentations of the actual position of the serves [40 and 142relative to the line being followed which position is stored in anincrement accumulator 162 and is utilized by the computer 28 inconjunction with the line segment information produced by thephotoelectric head 62 to determine the true position of the line and todrive the photoelectric head 62 to that position. The transducers 136and 138 have been shown connected to the servos 140, 142 in FIG. 7, butin actual practice they operate off of the beams as described above.

The increment accumulator 162 may consist of any conventional countingdevice such as a conventional flip-flop counter; in the preferredembodiment of this invention it was capable ofcounting 6667 per second.inch.

The line follower is. in its normal state, automatic in operation inthat it will follow a line from its beginning to its end at a rate ofi.p.m. or less while maintaining accuracies of 0.003 inch. It isnecessary for the follower to also have a manual control for the purposeof resolving ambiguities and for initiating a line following operation.However, within limits, the line follower can automatically resolve someambiguities and in addition can hunt for new lines to be followed.Ambiguities are defined to mean sharp corners occurring and returningwithin a given scanning area; they are also defined to include thecrossing of two lines in a scan area, a Teeing of lines and the like.

When the computer 28 determines from the information inputed to itthrough the chord position registers 156 that an ambiguity exists, thecomputer will cause the line follower 62 to stop if more than fourpoints intersect the circumference of the large circle within which theviewing or scanning circle moves. In this event, the computer will causethe tape typewriter 32 to print out the coordinates existing at thepoint of ambiguity, and at the same time will shift control of thedigitizing apparatus to the manual controls 90. Under normal conditionsof operation a line having dimensions will intersect the circumferenceofthe large circle at four points. Thus, ambiguities exist wherever morethan or less than four points are found in the large circle. Examples ofambiguities of more than four points are two lines intersecting withinthe circle (eight points), parallel lines of close proximity existingwithin the viewing circle (eight points), and the like.

On the other hand, ifthe ambiguity consists of broken lines or the endofa line, the computer will notice less than four line crossings or,that is, less than four points within the circle;

under these circumstances, the computer will stop data printout on therecorder 86, and will cause the servos to continue moving along thedirection of travel at the time the condition was detected, After anygiven number of scans, depending upon incrementing, if four points areagain detected, then normal automatic operation continues. On the otherhand, if less than four points are not detected, then the servos areautomatically stopped by the computer and control is shifted to manual.

The third common type of ambiguity consists of angle breaks, or i.e.,the sharp corners referred to above. As defined above, angle breaks aredefined as sharp corners occurring and returning within a given scanningarea. Within limits; the digitizing apparatus will automatically followangle breaks, however, in some cases, the angle is of such an acutevalue that it is impossible for the machine to follow it, in which case,the machine automatically stops and switches over to the manual modeofoperation.

The line follower is provided. in the preferred embodiment, with amanual mode of operation whereby an operator may override the computercontrol of the machine or the computer may switch over to manual asdefined above for the purpose of producing data representing thesolution of ambiguities and for initiating individual line followingoperations. To perform the mentioned functions the operator steers theline follower 62 with a plurality of controls located at the controlconsole 90. He can order the computer 28 to move the photoelectric head62 to any desired position over the line bearing article. The operatorscontrols include rough and fine photoelectric head positioning controlssuch as a joy stick and thumbwheels. The operator is also provided witha manual-automatic control switch, a start-stop control, recordcontrols, incrementing controls and the like. The operator is furtherprovided with an .enlarged picture ofthe total area contained within theviewing range of the line follower 62 on the TV receiver 82. The TVreceiver 82 obtains its display information from the photoelectric head62 where the di play information is such that the operator sees anenlarged view of the image seen by an optical system located in thephotoelectric head 62. The manner in which this image is obtained in thepreferred embodiment will be described subsequently.

in practice, the operator manually moves the photoelectric head 62 to astarting position by operating the joy stick and thumbwheels. He thendepresses record and increment keys on the program tape typewriter 32.The output from the tape typewriter 32 is read into the computer 28where the information is utilized by the computer to move thephotoelectric head 62 and to provide output information that is recordedon the recorder 86. If the line follower is in its automatic mode, itwill follow the chosen line automatically. Alternatively, the operatormay desire to manually follow the chosen line or to resolve anambiguity, in which case the line follower will move one incrementalstep after the operator has depressed the record and increment key andthen stop. The operator then can manually correct the position ofthephotoelectric head 62 to be precisely placed on the line. The operatorcan also control the feed rate or that is the incremental steppingofscanner unit 62 to larger increments than the 0.00l-inch movementstated heretofore.

The operator, in the preferred embodiment, can by placing the linefollower in a record only" mode freely wheel the scanner unit 62 towhatever position he desires. During both manual and automaticoperation, data representative of the movements of the photoelectricunit 62 are recorded on the recorder 86. Thus, it will be obvious thatthe operator can control the movements of the line follower when anambiguity occurs by instructing the follower to stop or when it stopsautomatically, whereupon he can manually resolve the ambiguity andreturn the follower to its automatic mode of operation.

Referring now to P16. 8, the photoelectric head 62 of the automaticdigitizing apparatus is shown in a side elevational view. Thephotoelectric head 62 looks at an image ofa portion of the articlecontaining lines or the like through a corrected lens 164 mounted in amovable and focusable lens holder 166. In the preferred embodiment, thearea under the scanner unit 62 is illuminated with artificial light byfour light projectors, not shown, mounted on the photoelectric head 62.it will be understood that various geometrical shapes of various sizesmay be observed by the scanner unit, and the size and shape of theobjective is a function of the degree of accuracy desired in theinformation output of the system.

The image seen by the lens is optically passed through and reflected offof a conventional beam splitter 168 to create two optical paths, 170 and172. The image on the path 170 is magnified and utilized for the purposeof providing the operator with an image of the area under the lens 166.The second optical path 172, or that is the reflected image, is utilizedto produce an electrical signal ir.dicating the position of a linesegment in the area under the lens system 166. The beam splitter 168passes a direct image of the area under observation along optical path170 to a lens system 174 which includes a reticle 176, as a sightingdevice. The image formed by the lens system 166 is focused on thereticle 176 and is passed from the reticle to a corrected lens 178 whichfocuses the image onto the target of an orthicon tube 180 or itsequivalent in a TV camera 182 to create a TV picture of the image seenby the lens system 166.

As an alternative to the TV camera on the path 170 a telescopicarrangement may be substituted. 1n such a case, the image focused on thetarget 180 of the Orthicon would be focused on a corrected lens systemutilized for altering the light path 170 by an angle of approximately90. The combined light path 170 would be similar to a periscope inreverse. in such a case a viewer mounted on one of the movable carriages16 or 18 of FIG. 1 could be focused on the light path 170, and in factwould be a continuation of the path. Thus, an image of the area underthe photoelectric head 62 can be made available to an operatorpositioned at the side of the table 10.

The image reflected off the beam splitter 168 along the optical path 172is focused by a corrected lens 184 mounted in a movable and focusablelens holder 186 onto a mirror 188. The mirror 188 reflects an image atan angle of 90 through a third corrected lens 190 contained within athird movable and focusable lens holder 192, through a pinhole diaphragm194 onto a target 196 of the photomultiplier tube 158. Since thediaphragm 194 is of the pinhole type it will only allow a portion of thebeam of light reflected from the mirror 188 to register upon thephotomultiplier target 196. The photomultiplier tube 158 isofconventional design and is utilized to produce an electrical signaloutput that will depend on the intensity of light reflected onto itstarget electrode 196. Thus, in the preferred embodiment, thephotomultiplier 198 will pulse every time the intensity of the beam,reflected off the mirror 188 along the path 172, changes.

In operation, the corrected lens 164 forms an image of a circle 200, asshown in FlG. 9, having a diameter of 0.080 inch and it is this imagethat the operator sees a magnified version of on his TV receiver 82through the use of the orthicon 180. In actual practice the lens system166 sees an area larger than the circle 200, FIG. 9, and the larger areais magnified and displayed on the receiver 82. The circle 200 isactually produced by the corrected lens 186 and exists only along theoptical path 172. But for the purpose of a description of an operationalembodiment of this invention, it will be assumed that the lens system166 images the circular area represented by the circle 200. The area asviewed by the photomultiplier tube 198 and eventually by the computer 28as will be described below is different in that it is determined by thesize of the opening in the pinhole diaphragm 194. It, in the preferredembodiment, consists of a circle 202 having a diameter of approximately0.012 inch, where the outside perimeter of this smaller circle is madetangential to the inside perimeter of the circular image (circle 200)seen by the lens system 166. If the entire image of the circle 200 werefocused on the PM tube 158, usable information could not be obtained inthe PM tube output. For this reason, the mirror 188 is caused to wobblein such a manner that the circle 202 appears to be rotating around theinside perimeter of circle 200. The manner in which the mirror 86 iscaused to wobble will be described below. The effect of the rotatingcircle 202 is achieved through the interaction of the mirror 188, thefixed angle of reflection along the optical path 172, and the use of thepinhole diaphragm 194. The effect of the rotating spot is important inthat, ifa line is assumed to exist in the field of vision of the lenssystem 166, that line must enter circle 200 at a definite point on itscircumference and leave the field of vision at some other definite pointon its circumference. The line will reflect light of a differentintensity than the material upon which it is drawn. Therefore a beam ofreflected light will change in intensity, if it moves in a circular pathwithin circle 200, every time it intercepts and leaves the line. Thislight is utilized in the photomultiplier tube 158 to produce pulses ofelectrical energy.

Referring now to FIG. 9, a segment ofa line 204, representing a linethat is being followed, is shown as an image on the surface of themirror 188. The circle 200 seen as an image by the lens I66 is shownhaving a Cartesian coordinate system superimposed on it, and is shown asan image on the surface of mirror 188 along with the image of the linesegment 204. This is the total image, with the exception of thoseportions of the line segment 204 lying outside the perimeter of themirror 188, that is reflected onto the mirror. The coordinate system issuperimposed for explanation purposes and its center coincides with thecenter of the circle 200. The mirror 188 is wobbled at a fixed cyclicrate so that the viewing circle 202 is caused to move at a constant ratearound the inside perimeter of circle 200. Thus at an arbitrary point intime light will be reflected onto the PM tube 158 when circle 202 hasits center located at coordinates X,,Y,,. In the preferred embodimentthe circle 202 is moved in a counterclockwise direction within circle200, thus the center of 202 will be atthe point X, Y, at somepredetermined time depending on the rate at which the mirror 188 wobbledafter the circle was at X,,Y,,.

Thus, in operation, a reflected viewing area is achieved in that, due tothe motion given to the mirror 188, a spot of reflected light appears tomake revolutions around the circumference of the circle 200 through allfour quadrants ofthe coordinate system at a definite cyclic repetitionrate. Each circuit of the circumference of the circle by the scanningarea constitutes a single scanning cycle. After each sweep thephotoelectric head 62, under the control of the computer 28, willcontinue to move in a direction computed to bring the direction ofmovement of the scanning unit into coincidence with the direction takenby the line segment 204.

As the circle 202 rotates it intercepts the leading edge of the linesegment 204 as at the point N,. The line segment has been shown ashaving width in FIG. 9 in that for practical purposes most drawn lineswould have width on the dimensional scales chosen. At the point ofinterception of the scanning area with the line segment, the intensityof light along the optical path 172 will change and will produce anelectrical pulse from the PM tube 158. The circular spot 202, incontinuing to rotate, will eventually leave the line at its trailingedge N, and thus the intensity of light on the path 172 will change asecond time to yield another electrical pulse. Likewise, during thescanning cycle, the light spot 202 must again intercept and leave theline segment 204 at the points N, and N, respectively and thus give offtwo more electrical pulses. When the spot has completed a full circuitof the circle, that is, has completed a scanning cycle, this fact mayalso be registered or indicated as a pulse of information and may bestored. This pulse is the reference pulse mentioned earlier and isobtained from the driving circuits for the mirror [88. These circuitswill be described subsequently.

In the preferred embodiment, the mirror 188 operates at a frequency of400 c.p.s., thus the circle 202 completes l revolution around the circle200 in 2.5 msec. This period is divided into increments which representpoints on the circle 201 described in circle 200 by the center point ofthe scanning circle 202. The number ofincrements chosen is a measure ofthe accuracy with which line segment 204 is located within circle 200.ln the preferred embodiment, a clock operating at 500 k.c.p.s. is usedto increment the circle 20! into 1,250 parts by utilizing the clockpulses to operate a plurality of counters indicated as the chordposition registers 156 in FIG. 7. When the scanning area 202 is at thezero point in a scanning cycle, that point being the point X,,Y,, in thecoordinate system, the counters register a zero count. Thus, when thescanning area reaches the point X,Y, this corresponds to a definitenumber of pulses outputted from the clock and to a correspondingpositive count on the registers. When the scanning area 202 firstintercepts the line 204 at N a definite pulse will be given off by thePM tube 198 and at this point the chord position counters will have alsoreceived a discrete number of pulses from the clock corresponding to adefinite number of increments on the circumference of the circle 201,described by the movement of the scanning circle 202. The pulse count isutilized as an indication of position of the leading edge of the linesegment 204 in the circle 200. Likewise, the pulse counts achieved atthe points N,, N,, and N are registered and thus the four points ofintersection of the line segment 204 with the circle 200 are determinedand available for use by the computer.

The computer averages these points to calculate a straight line segment206 which is an approximation of the centerline of the line segment 204.The averaging is accomplished by the computer in a manner well known inthe art. The computer 28 averages the numbers N, and N; to obtain anumber N,, which is representative of the intersection of the midpointof the line segment 204 with the circumference ofthe circle 201 and isin actuality the difference in the arc lengths N,X,, and N,X,, dividedby two. Likewise, the numbers N; and N are averaged to produce a numberN,, which is equal to the midpoint of the arc defined by the differenceof the arcs N,-,X,, and N,X,, di- -vided by two to give the second pointN,, on the circle. A line 206 drawnthrough the points N,, and N,, wiilhave, for all practical purposes, the exact direction of the linesegment 204 and, because of the very small area viewed by thephotoelectric head 62, is an excellent approximation of line segment204. As stated previously, it is anticipated that the line 204 may turnthrough a sharp corner within the circle defined by the optical system,or may terminate within the circle 200, or may be broken within thecircle 200, or may be intercepted by one or more lines within the circle200. In all cases such as this, an ambiguity will exist and may beresolved as discussed previously.

The direction of the line segment 206 is in general the direction inwhich it is desired that the line follower travel. When the center ofthe circle 200 is not on the line segment 206, then an offset error Eexists and is equal to the perpendicular distance between the line 206and the center ofthe circle 200. Under these conditions, it is desirableand necessary that the photoelectric head be made to move along a linesuch as the line N,,N, to intercept the line 206. The line N,,N, necessarily must pass through the center of the circle 200. Line N,,N, is inthe direction of line 206 and is inclined to line 206 forming anapproach angle A with it. The size of the angle of approach A is relatedto the offset error E by a gain factor G which is dependent on thecharacteristics of the servos 140, 142, and other mechanical constantsof the system. The line N,N,, is a fictional line stored in the memoryof the computer 28. it must satisfy the following conditions;

and A=GE The computer 28will establish a new line Nf,Na' based upon theinformation read in as a result of data produced during any givenscanning cycle. This is accomplished by computing the difference in thearcs N,,-N,, and N N where the difference in the two are lengths isrelated to and establishes a new approach angle A,. The computer alsosums the two arc lengths and divides by two to establish a chord lengthwhich is an approximation of the offset error E.

As has been stated, the scanning cycle starts from the point X,,Y,,which point is used by the computer to determine the coordinates of thecenter of the circle 200. Having obtained the offset error E as a chordlength equal to the perpendicular distance from the center of the chordN,,N,, the computer utilizes this information to compute the componenterrors X Y, and causes this point to be recorded, as the center point ofthe circle in combination with the end points of the chord N,,N,, andthus the drafting/digitizing apparatus in its digitizing mode avoids theproblem of printing out hunting signals represented by such informationas the exact position of the circle 200. The computer utilizes thisinformation to calculate the new line NflNd such that A=GE. Thesecomputations are easily handled by circuits well known in the computerart and therefore no further explanation of them is deemed necessary.When the line follower is operating in its automatic mode, the numbersincluding the variables described above are normally linear functions,but as E, the offset error number, approaches the radius of the viewingcircle in length, the functions become nonlinear. In such an event,directional line following correction information can be calculated byconventional nonlinear computer logic to adjust the direction of travelof the photoelectric head 62, and as an alternative an operator canswitch the line follower to its manual mode of operation and, throughthe use ofjoy sticks at his console. freewheel the head 62 back into alinear tracking mode and then switch the line follower back toautomatic.

It will ofcourse be recognized by those skilled in the art that othermethods of determining the position and direction of the line segment204 within the area 200 can be used. For example, if the point Nrepresents a precise calibrated arc length, and if a second point withinthe circle 200 is known, then the component distances from the secondpoint to N,, are related to these two points and can be found if theywere internally stored in the computer.

The above-described operations of the digitizing apparatus were givenwith respect to a line that was substantially straight. In mostpractical situations, wherein a user of this apparatus would desire tohave a line followed to produce a punch tape or other form of outputrecording the lines that will be followed in many cases will be roundedor will have circular parabolic geometry. in most practical situations,the user of the digitizing apparatus will want the machine to operate asfast as it is practicably possible to produce a record of the geometricfigure followed to a degree of accuracy compatible with the usualsituation to which the record is to be applied. That is to say, thenumber of points N,,N,, and other points determined by adding the centerof circle 200 to the offset error coordinates X,.Y,. taken from thecomputer will determine the degree of accuracy with which these linesapproach the line that is actually followed. Thus, the user may not wanta deviation greater than 2 mils from the real line or for a 1' inchcircle the allowable deviation may be no more than I mil. Thus, inactual practice, the computational registers of the computer 28 areprogrammed to print out or record those points that will remain withinthe user's tolerance requirements. In order to accomplish this, thecomputer may accept a plurality of points and as these points areaccepted by its computational registers, it will utilize the points todetermine the deviation taken by the line until a total computationequivalent to the tolerance level required has been achieved, at whichpoint the computer will instruct the recorder 86 to print out that pointat which the tole; ance level was reached.

The above referred to line number computations are directed by thecomputer 28 to the interpolator 72 and the electronic controls 132, 134for servos 140, 142 as a series of binary pulses which representincremental distance movements along the X and Y axes as shown in H0. 5.This information is also clock controlled in the output of the computer28 as to feed rate through the interpolator 72 and to the servoelectronics, thus delta X and delta Y represent servo rate of change ofdirection or, that is, velocity ratios, and the distance of travel alongthe two axes in the same manner as described with respect to thedrafting operation shown in H6. 6.

As stated heretofore, informational output is obtained by rotating andtilting the mirror 188 so that the photomultiplier 158 sees a viewingarea that appears to regularly move around the circumference of thecircle 200 seen by the lens 164.

PIEZOMOTOR Referring now to FIGS. 10 and 11, one embodiment of apiezomotor 150 for the mirror 138 is shown in a side elevational view.The mirror 188 is rigidly affixed to one end of a pressure-electric bar208. The piezobar 208 is a piezoelectric ceramic that will, whensubjected to an electrical signal, flex or bend in a manner well knownin the art; on the other hand, when a device of this type is flexed orbent, it will emit an electrical signal. Both principles are utilized inthe present invention for the purpose of wobbling the mirror 188. Thepiezobar 208 consists of a right circular cylinder of pressure-electricmaterial supported within an insulative casing 210 for circularvibrational motion around two vibrational nodal points 212, 214,intermediate ofthe end points 188, the mirror end of the bar 208 and216. The piezobar is coated with four longitudinally extendingelectrodes 218, 220, 222, and 224, placed at intervals of around thecircumference of the bar 208. These electrodes may be applied by anywell-known coating technique and in the preferred embodiment were coatedalong the entire length of the bar 208. A fifth ground electrode 226 ispositioned coaxially along the centeriine for the entire length of thepiezobar. Thus, electrical circuits can be established in the bar 208from any of the four surface electrodes 218, 220, 222 and 224 to thegrounding electrode 226.

The bar 208 is supported by a plurality of flexible electrical contacts228, 229 along an axis arbitrarily designated as the Y axis where thecontacts 228, 229 are in electrical conducting relationship with a pairof bar electrodes 218, 222. In a like manner, the bar 208 is supportedfor movement along the X axis by two pairs of contacts, not shown,electrically engaging electrodes 220, 224. The contacts electricallyconnect with the bar 208 at the nodal points 212, 214. Each contact 228of each pair of contacts is separated from the contact 229 of the samepair by a distance equaling one-half of the circumferential distancearound the bar 208. The contacts 228, 229 are electrically connected toand supported by bus bars 230, 231 respectively where bus bars 230, 231are anchored in and supported by a pair of insulative discs 232, 234.The discs 232, 234 are longitudinally displaced along the piezobar 208and are supported within and by the casing 210. Support discs 232, 234are provided with axial aligned bores 233 and 235 respectively withinwhich the piezobar 208 is supported for movement. The bores must belarge enough to allow the bar 208 to describe an ellipsoidal path. Thesupport discs 232, 234 are maintained in fixed spaced apart relationshipto one another by a pair of spacing bars 236, 238 which spacers may bemade out of conductive material and utilized to link bus bars 230 andcontacts 228 into a common electrical circuit and bus bars 231 andcontacts 229 into a second common electrical circuit. Support disc 234is anchored to casing 210 near end 216 of the piezobar 208 by suitableretaining means such as locking screw 240.

Casing 210 is internally threaded on one end to receive a threadedannular window holder 242. The holder 242 supports a window 244 which isaxially aligned with mirror 188 and is utilized to protect mirror 188,the piezobar and piezobar amplifier electronics from dust and likecontamination. The casing is supported on the other end in a secondinsulative casing 246. Casing 246 is provided with an annular recess inwhich casing 210 is seated whereby casing 210 is frictionally andrigidly attached to the casing 246. Casing 246 is provided with acentral circuit cavity 248 into which bus bars 230 and 231 extend andinto which spacer bars 236 and 238 may be extended. The circuit cavity248 is utilized to stack a plurality of circuit boards 250, 252 inmodule form. The bus bars 230 and 231 and the spacing bars 237 and 238,when used as conductors, extend through and are connected with piezobaramplifier circuits carried on the boards 250, 252.

A second cavity 254 is provided in casing 246 as a wiring cavity wherebyconductors may be linked up with circuit boards 250 and 252 throughcable port 256 in order that external piezoelectric ceramic drivercircuits are linked up with the piezobar amplifier circuits. Anysuitable means such as connecting plug 258 threaded into casing 246 andcommunicating with cavity 254 may be utilized for circuitinterconnections while maintaining the interiors of the circuit cavityand piezobar casing contamination free. In order to gain access to thecavities 248 and 254 and to remove the circuit boards and piezomotor asunits, a backing plate 260 is removably supported in an annular recess261 in the casing 246 and held there by a locking screw 262.

In operation, a driving signal of sinusoidal shape is applied to busbars 231 and thus to the piezobar electrodes through contacts 229.Assuming the signal to be such that it is zero and just startingpositive, then the bar 208 will start to bend, due to the inherentproperties of pressure electric materials. in the negative directionaround the nodes 212, 214. This motion becomes more pronounced as thesignal on electrode 222 becomes more positive. This action will causethe mirror 188 to tilt in the upward direction in that its placement isbeyond the node 212. The mirror 188 continues its upward motion until itreaches a peak simultaneously with the signal on electrode 222 reachinga maximum whereupon the mirror reverses its tilting direction as theelectrical input decreases. Obviously, if the polarity on electrode 222is reversed, then the direction of tilting ofmirror 188 will reversealong the Y axis.

Similarly, assuming the lack of a Y driving signal and a sinusoid inputon the X drive electrode 224, then the mirror 188 is tilted into and outofthe plane of the drawing shown in FIG. 10. Thus, if the signal on theX drive electrode is a maximum in either the positive or negativedirection and simultaneously the signal on the Y drive 222 is zero, thenthe mirror 188 will be tilted to a maximum into or out of the planeofthe drawing. As the X driving signal decreases in magnitude the mirrorwill decrease its angle of tilt into or out of the plane of the paper.If at the time the signal on the X electrode is increasing and if at thesame time the Y drive is receiving an increasingly positive signal, thenthe mirror 188 will tilt into or out of the plane of the paper andupward or downward simultaneously around node 212. It is believed fromthe foregoing description that it will be obvious to those skilled inthe art that when the signals on the driving electrodes are separated inphase by 90 that the motion of the circumference of the mirror will berotational and this is due to the tilting action given to the mirror 188by the piezobar 208. Thus it should be obvious that with this sort ofdrive applied to the bar 208 the area 202 on the circumference ofthecircle 200 imaged on the mirror 188 and brought into alignment with thepinhole v diaphragm along the path 172 will be progressively moving in atime varying manner and appears as a scanning circle moving at a steadycyclic rate around the circumference of the circle 200.

As the bar 208 flexes it will generate an electrical signal which signalis impressed upon contacts 228 from the electrode 218 for the Y axis andthe contacts, not shown, for the electrode 220 for the X axis. Thissignal is utilized for driving purposes in the crystal drive unit'selectronics, and is also utilized as a reference signal.

Referring now to FIG. 12, the driving circuits for the piczomotor 150are shown in block diagram form. The piezobar 208, as has been discussedpreviously, is provided with four electrodes, 218, 220. 222, 224,separated from each other by 90 of rotation around the circumference ofthe bar 208 and a fifth common electrode 226 coated on the inside baseofthe bar 208. The common electrode is grounded Electrode 218 isconnected through its bus bars to the input of the drive unitelectronics over line 264; this electrode was arbitrarily chosen as onthe Y axis. Similarly, X sense electrode 220 is connected to the driveelectronics over input line 266. Input line 264 is connected to theinput of a Y signal phase shifting network 268, to an emitter follower270, the operation and purpose of which will be described subsequently.An X signal phase shifter 272 is connected to the Y signal phase shifter268 over line 271. The X sensing line input 266 is connected to an AGCcontrol 274 for the X axis drive control. Automatic gain control for theY drive circuit is achieved by tapping phase shifter 268 in the Y drivenetwork with an AGC circuit 275. Phase shifters 268 and 272 shift thesignal impressed upon their inputs by and this signal is amplified in apair of power amplifiers where a power amplifier 278 is connected to theoutput of phase shifter 268 and a second power amplifier 280 isconnected to the output of phase shifter 272. AGC controls 274, 276 arealso applied to the power amplifiers 278, 280. The output of poweramplifier 278 is applied over line 282 to the Y axis drive electrode222. The output of power amplifier 280 is applied over line 284 to the Xaxis drive electrode 224.

Phase shifters 268, 272 receive as input signals sine wavesrepresentative of the flexed or bending state of the piezobar 208. Thesesignals are shifted in phase by 90 in phase shifter 268 and appliedafter amplification as Y drive signals over line 282. At the same time,in the preferred embodiment, the output of phase shifter 268 is appliedto the input of phase shifter 276 where the signal is shifted another 90in phase and is applied as X drive over line 284. Thus the signals onthe output lines are 90 out of phase with the inputs to the phaseshifter and 90 out of phase with each other, and therefore wobblingmotion is imparted to the mirror 188. Assuming the instantaneous pointsensed on the electrode 218 is a zero and a maximum negative signal hasbeen sensed on the electrode 220, then a shift of 90 along each axismeans next drive X pulse is a zero and the next drive Y pulse is amaximum positive. In actual practice, these static conditions of zeroand maximum output occur instantaneously and thus pulses are alwaysavailable for driving the piezobar 208 into different vibrational modes.

As has been explained heretofore, it is necessary that the computer 28,FIG. 1, be oriented with respect to the circle 200 under the lens system166 so that the computer will know when a scanning cycle has started andwhen it is finished or, that is, it must know where the informationaloutput is located relative to a coordinate system superimposed on thecircle 200. Any reference point may normally be chosen but in thepreferred embodiment of the invention, X maximum positive, Y zero(X,,Y,,) on a Cartesian coordinate system was chosen for this purpose.Thus, in FIG. 12, the emitter follower 270 is connected to the electrode218 to provide an output signal indicative of a Y zero condition. Thissignal is squared in pulse shaper 154 and transferred to a shiftregister, to be described below through a second emitter follower 286.It is pertinent to note at this point that since the output ofthepiezobar 208 is a sine wave, the output of a pulse sbaper 154 will be asquare wave having the periodicity of the sine wave and will be in phasewith the sine wave. Thus, the shift register or counter triggered by thesquared wave can be set to stop counting when the trailing edge of thepulse is received and can be utilized to transfer information to thecomputer. This information is utilized to orient the computer as to theposition of informational pulses on the circumference ofthe circle 200.

Referring now to FIG. 13, the electronics of the piezoelectric ceramicdriver unit are shown in schematic form. The complete subcircuits shownin block form in FIG. 12 are shown and contained within the dashed boxesof FIG. 13. All circuits shown in FIG. 13 are transistorized but, ofcourse, equivalent circuits could be substituted utilizing vacuum tubesand, of course, the transistors shown as NPN devices could have PNPcircuits substituted for those shown and NPN circuits could besubstituted for the PNP circuits shown.

The phase shifter 268 connected to line 264 comprises a split load phaseinverter 288 having conventional bias circuitry and having outputs fedfrom the collector and emitter of a transistor 290 to an RC phaseshifting circuit 292 located in the input circuit of a conventionalemitter follower 294. The RC time constants in the base circuit ofemitter follower 294 are such that the output of the split load phaseinverter 288 is shifted in phase by 90. The output of inverter 288 isalso applied to the input of a silicon bridge rectifier 296 to develop aDC signal to be applied to the emitter of a field effect transistor 298for automatic gain control purposes.

The output signal from the emitter follower 294 is developed across a Ygain setting potentiometer 300 and applied as an input signal to thefirst stage of the two-stage cascaded power amplifier 278. The poweramplifier 278 utilizes two cascaded stages 302, 304, of poweramplification in order to obtain two phase reversals of the signalapplied to the base of amplifier 302 so that the signal on Y drive line282 is in phase with the output of the phase shifter 288, and the useoftwo stages of power amplification, of course, increases the drivingpower to the piezobar.

Both power amplifier stages utilized conventional biasing networks andcoupling networks and no further explanation of them is deemednecessary,

The signal developed across the gain setting potentiometer 300 isapplied as a signal source to a series circuit consisting of theresistor 306 and the two bases of the FET 298. The output of theinverter 288 is applied to the bridge rectifier 296 to produce full waverectification of the signal. The rectified signal is impressed acrossthe emitter and grounded base of the FET for bias purposes. The FET thusis made to act like an automatic potentiometer in that by changing theemitter bias the impedance between the emitter and grounded base isvaried to cause the impedance from the ungrounded base to ground tochange. In this manner the voltage drop across the FET is varied inaccordance with the amplitude of the applied emitter bias. As a gainregulator the RMS value of the signal developed across the FET remainsessentially constant in that as the emitter bias decreases the impedanceof the FET iricreases causing the voltage drop across the two bases toremain the same. Conversely, if the signal input to the bridgeincreases, the impedance of the FET decreases, thus decreasing thevoltage drop across the two bases causing the output to remain constant.The voltage developed across the FET is applied as an input signal tothe first stage 302 of the power amplifier 278.

Thus, it will be obvious to those skilled in the art that the amplitudeof signal applied to the input of the power amplifier will, within theoperating limits of the automatic voltage control circuit, beapproximately the same except for the inherent signal attenuatingeffects of the circuitry employed and will differ from the input signalapplied to the drive circuit by a shift in phase of 90.

X axis drive is obtained by slaving the phase shifter 272 to the outputof emitter follower 294 in the Y phase shifter circuit 268. This methodof obtaining drive for the X drive electrode 224 was adopted in thepresent embodiment for expediency; methods such as the duplication of Ydrive circuits could have been utilized but this would have requiredphase comparison circuits to insure a 90 phase separation between the Xand Y drivers. The phase shifter 272 is similar in operation andconstruction to that described above with respect to the phase shifter268. A split load phase inverter 308 has signal input applied to itsbase from a connection taken at a junction 310 of the emitter of emitterfollower 294 and potentiometer 300. The output of the phase inverter 308is applied to both ends of an RC phase shifter consisting ofcapacitor312 and rheostat 314. Thus, by slaving the X driver to the Y driver a 90phase separation between the two drive signals is easily obtained byadjusting rheostat 314 and therefore adjusting the time constant of theX drive phase shifter. The X drive signal is phase shifted by 90 and isapplied to the base of an emitter follower 316. The output signal of theemitter follower 316 is developed across an X axis gain setting pot 318and is applied to base 2 of an FET 320 in the AGC circuit 274 ofthe Xdriver and to the input of power amplifier 280 which consists of twocascaded stages 322, 324 of power amplification and is similar inoperation to power amplifier 278 described above.

DC input for FET emitter control is obtained by applying the signalsensed on electrode 220 over line 266 to the base of a split load phaseinverter 326 for the purpose of developing a drive signal to the inputsof a silicon bridge rectifier 328. The output of the bridge rectifier328 is a DC signal which is applied to the emitter of the FET 320. Base2 of the FET 320 is connected to potentiometer 318 through resistor 320and automatic gain control is achieved in the same manner as describedabove with respect to the Y drive AGC stage 276. The amplified phaseshifter X drive signal is applied over line 284 to electrode 224.

As mentioned previously, the output of piezobar 208 is sinusoidal and isutilized to orient the computer 28 as to the position of a line withinthe viewing circle 200 imaged by the lens system 166. For the purposeofproviding this signal to the computer, the Y sense electrode 218 isconnected to the input of the emitter follower 270. The bias circuits ofthe emitter follower are conventional. The output signal of the followeris developed in emitter resistor 332 and applied over line 334 to theinput of a squaring circuit, which may be a conventional Schmidttrigger, 154. The squared signal in the output of the Schmidt trigger isapplied to the input registers of computer 28 through emitter follower286.

Referring now to FIG. 14, the input circuits from the photomultiplier158 for the computer 28 are shown in block diagram form. The output ofthe PM tube 158 consists of a series of pulses where each pulserepresents a change in light value on the target 196 of the PM tube 158.As has been explained, these changes occur every time the scanning spot202 intercepts the line being followedand again when the scanning spotleaves the line. The computer input circuits are designed so that theywill accept and register the output of the photomultiplier whether thatoutput is produced by a dark line located on a light reflecting surfaceor a light reflecting line located on a light absorbing surface or aline representing a transitional state between two bodies having adifferent light reflecting properties. The output of the photomultiplieris applied to a squaring circuit 160 which may consist of a conventionalSchmidt trigger. Other pulse producing circuits could be readilysubstituted for the Schmidt trigger used in the preferred embodiment.The squarer 160 is utilized for the purpose of shaping the pulsesproduced by the photomultiplier 158 into a squared waveform so that theymay be used to trigger binary circuits.

The squared output of the pulse shaper 160 is applied after currentamplification in a pair of emitter followers 336, 338 to the chordposition register 156 through a discriminator 340 and stepping switch342. The chord position register 156 consists of five shift registers344, 346, 348, 350, and 352 which may be of any conventional shiftregister design such as a ring of flip-flops, SCRs or the like, and areused as counters. The stepping switch 342 applies the squared output ofthe multiplier to each of four of the shift registers 344, 346, 348, and350 in time sequence. in the preferred embodiment, five counters areemployed in that five signals are contemplated, four of which aregenerated by the viewing area 202 when the circle crosses a line locatedwithin the circle 200 as seen by the lens system 166; the fifth signalis generated when the viewing area 202 completes one scanning cycle, thesignal is produced on line 334. The discriminator 340 is utilized forthe purpose of moving the input on the chord position register 156 tothe counter 346 as the starting counter when the special circumstance ofthe line segment 204, see H6. 9, lies on the X axis or partially on theX axis so that a scanning cycle commences with the viewing area 202located on or within the line segment. ln that it is contemplated thatin normal operation as stated heretofore, the viewing area 202 wouldfirst intercept the line segment 204 at some other position in thecircle 200 and assuming a normal situation of a line segment being of adark color on a light background, then in that case, the change

1. A photoelectric system for imaging drafted information contained onsheetlike articles to produce output information representative of theposition and direction of said drafted information on said articlescomprising: means for illuminating a discrete area on said article;first optical means for forming an image of said discrete area; meansincluded in an optical path with said first optical means for splittingsaid image of said discrete area into two images along first and secondoptical paths; second optical means included in a first optical pathwith said image splitting means for generating an electrical analog ofone of said images formed by said beam splitting means; third opticalmeans included in a second optical path with said image splitting meansfor progressively testing the other of said images produced by said beamsplitting means to determine the position and direction of draftedinformation contained within said discrete area imaged by said firstoptical means; and means in said second optical path for generatingelectrical signals indicative of the position and direction of draftedinformation contained within said discrete area.
 2. A photoelectricsystem for imaging drafted information contained on sheetlike articlesto produce output information representative of the position anddirection of said drafted information on said articles comprising; meansfor illuminating a discrete area on said article; first optical meansfor forming an image of said discrete area; means included in an opticalpath with said first optical means for splitting said image of saiddiscrete area into two images along first and second optical paths;second optical means included in said first optical path with said imagesplitting means for generating a television picture out of one of saidimages formed by said beam splitting means; third optical means includedin said second optical path with said image splitting means forprogressively testing the other of said images produced by said beamsplitting means to determine the position and direction of draftedinformation contained within said discrete area; and means in saidsecond optical path for generating electrical signals indicative of theposition and direction of drafted information contained within saiddiscrete area.
 3. A photoelectric system for imaging drafted informationcontained on sheetlike articles to produce output informationrepresentative of the position and direction of said drafted informationon said articles comprising: an illuminator positioned above a sheetlikearticle and having at least one source of light for illuminating adiscrete area on said article; a first corrected lens system for imagingsaid discrete area; a beam splitter in an optical path with saidcorrected lens system for splitting said optical path into at least twooptical paths; a television camera for producing an electrical analog ofsaid discrete area; a second corrected lens system including a reticlein a first optical path with said beam splitter and said televisioncamera for magnifying and superimposing a grid on said optical image;and a third corrected lens system, including a rotating mirror, apinhole diaphragm anD a photomultiplier tube in a second optical pathwith said beam splitter to produce an electrical pulse outputrepresentative of the position and direction of drafted informationcontained within said discrete area.
 4. In a photoelectric system forimaging along an optical path drafted information contained on asheetlike article to produce output information representative of theposition and direction of said drafted information on said articles, anoptical scanning device comprising: a piezoelectric ceramic, capable ofbeing driven into states of mechanical stress by electrical signals andcapable of generating electrical signals indicative of the state ofmechanical stress in which said piezoelectric ceramic has been placed,having a plurality of electrodes to which electric drive signals areapplied and from which stress sense signals are obtained; means forelectrically driving said piezoelectric ceramic into a state of stress;means for connecting said driving means to said electrodes; means forelectrically sensing the state of stress of said piezoelectric ceramic;means for connecting said sensing means to said electrodes on saidpiezoelectric ceramic; and optical means, included in said optical pathin said photoelectric system, affixed to said piezoelectric ceramic forchanging the transmitted image along said optical path in accordancewith the stressed states of said piezoelectric ceramic.
 5. In aphotoelectric system for imaging along an optical path draftedinformation contained on a sheetlike article to produce outputinformation representative of the position and direction of said draftedinformation on said articles, an optical scanning device forprogressively testing discrete areas on said article to determine thelight reflecting ability of time-spaced points within said discreteareas comprising: a piezobar having a plurality of driving and sensingelectrodes equally spaced around the periphery of said piezobar, andhaving a grounding electrode; circuit means for driving said piezobarinto states of stress and for sensing the states to which said piezobaris driven; conductor means for electrically connecting said piezobar tosaid circuit means; optical means, included in said optical path,mounted on said piezobar, for transmitting an image in said opticalpath, said optical means being wobbled by said piezobar in atime-varying manner; an output device; and means connected to a sensingelectrode on said piezobar for transmitting an electrical signalgenerated by said piezobar to said output device.
 6. In a photoelectricsystem for imaging along an optical path drafted information containedon a sheetlike article to produce output information representative ofthe position and direction of said drafted information on said articles,an optical scanning device comprising: a piezobar having a plurality ofequally spaced driving and sensing electrodes extending longitudinallyalong the outer surface of said piezobar and having a coaxiallyconcentric grounding electrode; first circuit means connected to saidsensing electrodes for detecting electrical signals generated by saidpiezobar; second circuit means including a first phase shifter connectedto said first circuit means for shifting said sensed signal in phase andfor applying the resulting phase shifted signal as a time-varying signalto at least one driving electrode on said piezobar; third circuit meansincluding a phase shifter connected to the output of said first phaseshifter for shifting the output of said first phase shifter in phase andfor applying the resultant signal as a time-varying signal to a seconddriving electrode; an output device; means connected to a sensingelectrode for transmitting an electrical signal generated by saidpiezobar at said electrode to said output device; and optical means,included in said optical path, mounted on said piezobar for transmittinga time-varying image along said optical path when said piezobar issubjected to time-varying stress signals.
 7. In a photoelectric systemfor imaging along an optical path drafted information contained on asheetlike article to produce output information representative of theposition and direction of said drafted information on said articles, anoptical scanning device comprising: a piezobar having a plurality ofelectrodes on the outer surface thereof and having a groundingelectrode; a mirror included in said optical path mounted on one end ofsaid piezobar; a support member; a plurality of electrical contactsengaging the electrodes on said piezobar to support said piezobar forflexible movement within said support member; a plurality of piezobardrive and sense circuits; and electrical conducting means connected tosaid electrical contacts for connecting said electrodes to said piezobardrive and sense circuitry.
 8. In a photoelectric system for imagingalong an optical path drafted information contained on a sheetlikearticle to produce output information representative of the position anddirection of said drafted information on said articles, an opticalscanning device comprising: an elongated cylindrical piezobar having aplurality of longitudinally extending electrodes, spaced around theouter surface of said piezobar, and having a grounding electrodecontained within and concentric of said piezobar; a mirror rigidlymounted on one end of said piezobar; a plurality of electrical contactsengaging the electrodes of said piezobar to support said piezobar forflexible movement within a pair of fixed spaced apart discs, saidcontacts being anchored in said discs; an elongated cylindrical outercasing for supporting said piezobar, said casing being enclosed at oneend by a window element in alignment with a light-reflecting surface ofsaid mirror, and at the other end by a hollow boxlike member havingsidewalls and a removable end wall; a pair of disc members mounted insaid elongated cylindrical casing, said disc members beinglongitudinally spaced apart from each other in said casing; a pluralityof electrical contacts mounted in said spaced apart discs, saidelectrical contacts engaged in the electrodes of said piezobar forsupporting said piezobar for flexible movement within said discs; aplurality of circuit boards mounted in said boxlike member and supportedin fixed spaced apart relation by the sidewalls of said boxlike member;and a contact board mounted on one sidewall of said boxlike member forextending electrical circuits mounted on said circuit boards to circuitslocated outside of said boxlike member.
 9. In a machine for digitizing aline drawn on a sheetlike article to produce digital data representativeof the position and direction of said line on said article, and havingan optical scanning member, a driving system for said optical scanningmember comprising: first electrical means connected to said opticalscanning member for receiving a signal from said optical scanning memberand for shifting said signal in phase by a predetermined amount; firstamplifier means connected to said first electrical means for amplifyingsaid phase shifted signal; means connected to said first amplifier meansfor applying said phase shifted signal to said optical scanning memberas a drive signal; second electrical means connected to said firstamplifier means for shifting said phase shifted signal in phase by asecond predetermined amount; second amplifier means connected to saidsecond electrical means for amplifying said second phase shifted signal;and means connected to said second amplifier means for applying saidsecond phase shifted signal to said optical scanning member as a drivesignal.
 10. In a machine having automatic control circuits fordigitizing a line drawn on a sheetlike article to produce digital datarepresentative of the position and direction of said line on saidarticle, and having an optical scanning member, a driving system forsaid optical scanning member comprising: first electrical meansconnected to said optical scanning member for reCeiving a signal fromsaid optical scanning member and for shifting said signal in phase by apredetermined amount; first amplifier means connected to said firstelectrical means for amplifying said phase shifted signal; meansconnected to said first amplifier means for applying said phase shiftedsignal to said optical scanning member as a drive signal; first voltagecontrol means connected to said first electrical means and said firstamplifying means for automatically controlling the signal level of saidphase shifted signal applied to said means for applying said phaseshifted signal to said optical scanning member; second electrical meansconnected to said first amplifier means for shifting said phase shiftedsignal in phase by a second predetermined amount; second amplifier meansconnected to said second electrical means for amplifying said secondphase shifted signal; means connected to said second amplifier means forapplying said second phase shifted signal to said optical scanningmember as a drive signal; second voltage control means connected to saidoptical scanning member and to said second amplifying means forautomatically controlling the signal level of said second phase shiftedsignal applied to said second means for applying said phase shiftedsignal to said optical scanning member; and third electrical meansconnected to said optical scanning member and said line digitizer forapplying a signal indicative of the operational status of said opticalscanning member to the control circuits of said line digitizer.
 11. In amachine having automatic control circuits for digitizing a line drawn ona sheetlike article to produce digital data representative of theposition and direction of said line on said article, and having anoptical scanning member, a driving system for said optical scanningmember comprising: a first electronics phase shifting circuit connectedto said optical scanning member for receiving an electrical signal fromsaid optical scanning member and for shifting said signal in phase by apredetermined number of degrees; a first emitter follower connectedbetween said optical scanning member and the automatic control circuitsof the machine for transferring an electrical signal output of saidoptical scanning member to said control circuits; a second emitterfollower connected to said first phase shifter for amplifying said phaseshifted signal; a first automatic voltage control circuit connected tosaid first phase shifter and said second emitter follower forcontrolling the signal level of said phase shifted signal; a first poweramplifier connected to said automatic voltage control circuit and saidoptical scanning member for amplifying said phase shifted signal andapplying same to said optical scanning member; a second electronicsphase shifter connected to said second emitter follower for shiftingsaid phase shifted signal in phase by a second predetermined number ofdegrees; a third emitter follower connected to said second phase shifterfor amplifying said second phase shifted signal; a second automaticvoltage control circuit connected to said optical scanning member andsaid third emitter follower for controlling the signal level of saidsecond phase shifted signal; and a second power amplifier connected tosaid second automatic voltage control circuit, and said optical scanningmember for amplifying said second phase shifted signal and for applyingsame to said optical scanning member.